> FB 1.5
>
> I have a UDF declared like this:
>
> DECLARE EXTERNAL FUNCTION F_ENCODE_HTML
> CSTRING(4096)
> RETURNS CSTRING(4096) FREE_IT
> ENTRY_POINT 'Str_EncodeHTML' MODULE_NAME 'Primavera_UDF';
>
> Its function is to escape protected HTML chars like "&" or "<".
>
> If I use it like this:
>
> **********
> Select F_ENCODE_HTML( Substring(<some memo field> from 1 for 4096)
> from <some table>
>
> ***********
>
> it works ok until I get to a memo that contains more than 256
> characters where it fails with "...string overflow". This happens
> even with the memo is well below 4096 but greater than 256.
>
> if I change the substring part to "from 1 to 256" it runs ok,
> but "from 1 to 257" fails.
>
> Then I read something about how another substring UDF function did
> not work properly until the max size of CSTRING was used in the
> UDF. So I changed the definition to:
>
> DECLARE EXTERNAL FUNCTION F_ENCODE_HTML
> CSTRING(32767)
> RETURNS CSTRING(32767) FREE_IT
> ENTRY_POINT 'Str_EncodeHTML' MODULE_NAME 'Primavera_UDF';
>
> and it works with memos larger than 256.
>
> Can anyone explain this?

Seems like bug in your UDF (missing or incorrectly set terminating zero character)

Ivan